I must burrow you must burrow she must burrow we must burrow you must burrow they must burrow
V-ing form
I must be burrowing you must be burrowing she must be burrowing we must be burrowing you must be burrowing they must be burrowing
Perfect
I must have burrowed you must have burrowed she must have burrowed we must have burrowed you must have burrowed they must have burrowed
V-ing perfect
I must have been burrowing you must have been burrowing she must have been burrowing we must have been burrowing you must have been burrowing they must have been burrowing
Negation
Simple form
I mustn't burrow you mustn't burrow she mustn't burrow we mustn't burrow you mustn't burrow they mustn't burrow
V-ing form
I mustn't be burrowing you mustn't be burrowing she mustn't be burrowing we mustn't be burrowing you mustn't be burrowing they mustn't be burrowing
Perfect
I mustn't have burrowed you mustn't have burrowed she mustn't have burrowed we mustn't have burrowed you mustn't have burrowed they mustn't have burrowed
V-ing perfect
I mustn't have been burrowing you mustn't have been burrowing she mustn't have been burrowing we mustn't have been burrowing you mustn't have been burrowing they mustn't have been burrowing
Interrogative form
Simple form
must I burrow? must you burrow? must she burrow? must we burrow? must you burrow? must they burrow?
V-ing form
must I be burrowing? must you be burrowing? must she be burrowing? must we be burrowing? must you be burrowing? must they be burrowing?
Perfect
must I have burrowed? must you have burrowed? must she have burrowed? must we have burrowed? must you have burrowed? must they have burrowed?
V-ing perfect
must I have been burrowing? must you have been burrowing? must she have been burrowing? must we have been burrowing? must you have been burrowing? must they have been burrowing?
Interro-negative form
Simple form
mustn't I burrow? mustn't you burrow? mustn't she burrow? mustn't we burrow? mustn't you burrow? mustn't they burrow?
V-ing form
mustn't I be burrowing? mustn't you be burrowing? mustn't she be burrowing? mustn't we be burrowing? mustn't you be burrowing? mustn't they be burrowing?
Perfect
mustn't I have burrowed? mustn't you have burrowed? mustn't she have burrowed? mustn't we have burrowed? mustn't you have burrowed? mustn't they have burrowed?
V-ing perfect
mustn't I have been burrowing? mustn't you have been burrowing? mustn't she have been burrowing? mustn't we have been burrowing? mustn't you have been burrowing? mustn't they have been burrowing?